S225: CIRCULATING TUMOR DNA IS A PROGNOSTIC BIOMARKER AT BASELINE AND IMPROVES THE ACCURACY OF INTERIM PET IN CLASSIC HODGKIN LYMPHOMA
Authors: M. C. Pirosa, A. Bruscaggin, L. Terzi di Bergamo, M. Salehi, K. Pini, V. Spina, S. Bocchetta, A. Condoluci, G. Forestieri, D. Piffaretti, J. Marques De Almeida, S. Annunziata, F. Bergesio, E. Borsatti, P. Bulian, S. Chauvie, C. Marco, D. T. Martina, G. Bernhard, M. Kurlapski, A. Moccia, R. Moia, A. Rinaldi, M. Rodari, G. Romanowicz, G. M. Sacchetti, A. Stasia, A. Stathis, G. Stüssi, I. Zangrilli, L. M. Larocca, A. Pinto, A. Santoro, F. Cavalli, E. Zucca, V. Gattei, J. M. Zaucha, C. Carlo-Stella, S. Hohaus, G. Gaidano, L. Ceriani, D. Rossi
Journal: HemaSphere (2022)

Background: Classic Hodgkin lymphoma (cHL) has few pre-treatment prognostic biomarkers. Circulating tumor DNA (ctDNA) is a metrics of tumor volume and inflammation, which are both prognostic in cHL, it improves the accuracy of treatment response assessment, which is an unmet need at the interim timepoint in cHL, and it allows to accurately genotype the disease, which has technical hurdles if done of the tumor biopsy in cHL. Aims: The study aims at addressing the following questions: i) is pre-treatment ctDNA load a metrics that captures both tumor and inflammation extents in a single, measurable and radiation-free test? Can the integration of ctDNA with interim PET (iPET) improve accuracy of the sole iPET in predicting treatment outcome? Can ctDNA identify molecular groups with phenotype- and outcome-associated signatures? Methods: IOSI-EMA003 (NCT03280394) is a prospective, observational, multi-center study. The study recruited adult patients with previously untreated cHL. Blood samples were collected during staging and disease response assessment at the same time of PET scan acquisition. PET scans were centrally and blindly reviewed by a panel of nuclear medicine physicians. ctDNA was genotyped and quantified by phased variant-enhanced-LyV4.0 ctDNA CAPP-seq assay. Interim molecular response (iMR) was defined as lack tumor reporters in cfDNA collected at the interim timepoint (sensitivity 10-4). Results: A total of 215 patients were recruited. Median follow-up was 30 months. The full analysis dataset was divided into training (N=135) and validation (N=80) cohorts by using a random sample procedure. In the training cohort, ctDNA load directly associated with inflammation (B symptoms, elevated ESR), but not with disease burden: total metabolic tumor volume (TMTV), GHSG stage. The optimized threshold of pretreatment ctDNA load to stratify PFS was 850 hGE/mL of plasma (Figure 1A). In multivariable analysis, pretreatment ctDNA levels remained prognostic for PFS when controlling for either GHSG stage, TMTV, B symptoms or ESR. The validation cohort confirmed that patients with higher pretreatment ctDNA levels had inferior PFS (Figure 1B). Among intermediate and advanced stage patients, the PFS of patients with positive iPET was significantly inferior (Figure 1C). iMR was achieved in 54% patients. Patients who did not achieved iMR had a lower PFS. iMR combined with iPET had a statistically significant superior accuracy for the anticipation of progression or relapse compared to iMR or iPET alone (Figure 1D). To identify molecular subgroups within cHL, we focused on fragmentation profiles of cfDNA. cfDNA fragmentome can comprehensively represent both genomic and chromatin characteristics. Pre-treatment cfDNA fragmentation patterns were characterized by a more prominent mononucleosomal fragments abundance in 51% of patients (mono-nucleosomal cluster), whereas 33% of patients had a more prominent shift towards submono-nucleosomal fragment lengths (submono-nucleosomal cluster) (Figure 1E). Patients belonging to the submono-nucleosomal cluster had different clinical and biological nuances, including advanced stage, B-symptoms, elevated ESR, higher TMTV and total lesion glycolysis, higher mutation load, higher circulating immune suppressive cytokines and chemoattractants for monocytes and Th-cells. Accordingly, patients with submono-nucleosomal cluster had a lower PFS. Image:Summary/Conclusion: ctDNA is a validated prognostic biomarker of cHL, can improve the accuracy of interim response assessment and provide the bases for a molecular classification of cHL.